Thin film evaporation heat dissipation device that prevents bubble formation

ABSTRACT

Apparatus for removing heat from a heat generating device comprising a two-phase heat dissipation device having a dispersion device disposed within the heat dissipation device. The heat dissipation device includes a sealed housing having a vaporization region within the sealed housing and a condensation region within the sealed housing, a working fluid disposed within said seal housing; and the dispersion device being adapted to disperse said working fluid toward the sealed housing vaporization region. The heat dissipation device may further include a divider plate dispose within the sealed housing, wherein the divider plate substantially divides the sealed housing into a vapor path chamber and a liquid path chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to heat dissipation devices. In particular, an embodiment of the present invention relates to a two-phase (liquid/vapor), forced convection heat dissipation device that disperses a working fluid, which results in the prevention of bubble formation and/or creation of a thin film of the working fluid on an evaporation region for improved evaporation thereof.

2. State of the Art

The microelectronic device industry continues to see tremendous advances in technologies that permit increased circuit density and complexity, and equally dramatic decreases in package sizes. Such high density and high functionality in these microelectronic devices has resulted in an increase in the density of the power consumption by the integrated circuit components in the microelectronic device, which, in turn, increases the average junction temperature of the microelectronic device. If the temperature of the microelectronic device becomes too high, the integrated circuits within the microelectronic device may be damaged or destroyed.

Various apparatus and techniques have been used and are presently being used for removing heat from microelectronic devices. One known method of removing heat from a microelectronic device is the use of a heat pipe 300, as shown in FIG. 6. A heat pipe 300 is a simple device that can quickly transfer heat from one point to another without the use of electrical or mechanical energy input. The heat pipe 300 is generally formed by evacuating air from a sealed pipe 302 that contains a “working fluid” 304, such as water or alcohol. The sealed pipe 302 is usually constructed from a thermally conductive material, such as copper, copper alloys, aluminum, aluminum alloys, and the like, and oriented with a first end 306 proximate a heat source 308. The working fluid 304, which is in a liquid phase proximate the heat source 308, increases in temperature and evaporates to form a vapor phase of the working fluid 304, which moves (shown by arrows 312) toward a cooler, second end 314 of the sealed pipe 302. As the vapor phase moves toward the sealed pipe second end 314, it condenses to again form the liquid phase of the working fluid 304, thereby releasing the heat absorbed during the evaporation of the liquid phase of the working fluid 304. The liquid phase returns, usually by capillary action, gravity (thermosiphon), or a wick 316 to the sealed pipe first end 306 proximate the heat source 308 (shown by arrows 318), wherein the process is repeated. Thus, the heat pipe 300 is able to rapidly transfer heat away from the heat source 308 and requires no external driving force other than a temperature differential.

However, with the ever increasing temperature, simple heat pipes are not capable of removing sufficient heat from microelectronic device, as current heat pipe designs suffer from low critical heat flux and high evaporator resistance, as will be understood to those skilled in the art. Improvements to heat pipes, such as forced convection with pumps and/or microchannels, can be implemented. However, these improvements have not been entirely successful. Pumps are not sufficiently reliable and microchannels can develop liquid slugs in the vapor portion of the microchannel which blocks the vapor flow to the condensation end of microchannel causing partial or total dry-out condition resulting in heat transfer failure. Furthermore, using more complex cooling methods, such cryogenic cooling or refrigeration cooling are too expensive for use in high volume commercial electronic devices.

Therefore, it would be advantageous to develop heat dissipation device designs having an improved critical heat flux and lower evaporator resistance, while still having using simple components.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, the advantages of this invention can be more readily ascertained from the following description of the invention when read in conjunction with the accompanying drawings to which:

FIG. 1 is a side cross-sectional view of an embodiment of a thin film evaporation heat dissipation device, according to the present invention;

FIG. 2 is a side cross-sectional view of another embodiment of a thin film evaporation heat dissipation device, according to the present invention;

FIG. 3 is a side cross-sectional view of a thermosiphon configuration of a thin film evaporation heat dissipation device, according to the present invention;

FIG. 4 is a side cross-sectional view of another embodiment of a thin film evaporation heat dissipation device, according to the present invention;

FIG. 5 is an oblique view of a computer system having a heat dissipation device of the present integrated therein, according to the present invention; and

FIG. 6 is a side cross-sectional view of a heat pipe/vapor chamber, as known in the art.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein, in connection with one embodiment, may be implemented within other embodiments without departing from the spirit and scope of the invention. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled. In the drawings, like numerals refer to the same or similar functionality throughout the several views.

An embodiment of the present invention comprises a two-phase (liquid/vapor) heat dissipation device to remove heat from a heat generating device, wherein the heat dissipation device has an internal dispersion device (e.g., a rotating device, such as a fan) and is adapted to decrease boiling resistance and increase the critical heat flux.

FIG. 1 illustrates a heat dissipation device 100 according to the present invention. The heat dissipation device 100 may comprise a sealed housing 102, which may be constructed of conductive material including, but not limited to, copper, copper alloys, aluminum, aluminum alloys, and the like. A first external portion 104 of the sealed housing 102 thermally contacts a heat generating device 106, such as a microelectronic device (e.g., central processing units (CPUs), chipsets, memory devices, ASICs, and the like). A dispersion device 108 (e.g., a rotating device, such as a fan) may be positioned within the sealed housing 102 proximate the heat generating device 106.

A working fluid 112 within the sealed housing 102, when in a liquid phase, is a dispersed by the dispersion device 108 as a liquid spray toward a vaporization region 114, within the sealed housing 102, proximate the heat generating device 106. The working fluid 112 liquid spray is dispersed substantially uniformly to form a thin layer on the vaporization region 114. Thus, the vaporization region should be substantially continuously wetted with the working fluid 112. Furthermore, the dispersion device 108 “flattens” substantially all working fluid bubbles before they can form. If such working fluid bubbles form, they impede the working fluid from wetting the vaporization region 114, which greatly reduces the efficiency of the heat dissipation device 100.

The working fluid 112 may include, but is not limited to water, Freon, acetone, alcohol, and the like. The heat from the heat generating device 106 is transferred through the sealed housing 102 by conductive heat transfer. This heat vaporizes the working fluid 112 liquid film into a vapor phase within the vaporization region 114. The vapor phase of the working fluid 112 substantially follows along a path illustrated by arrows 116 in FIG. 1 to a cooler, condensation region 122 within the sealed housing 102. The vapor phase of the working fluid 112 condenses in the condensation region 122 to form a liquid phase. During the condensation process, the heat absorbed during the evaporation of the liquid phase of the working fluid 112 is released and the released heat is transferred to the sealed housing 102 proximate the condensation region 122. The sealed housing 102 may be evacuated to at or near vacuum condition. The pressure condition within the sealed housing 102 is, of course, dependant on the working fluid 112 used. For example, if the working fluid 112 is water, the sealed housing 102 may have a pressure between about 10-50 kPa. If the working fluid is Freon (i.e., R134a), the pressure can be between about 600-700 kPa.

In a heat pipe or vapor chamber configuration of the heat dissipation device 100, the liquid phase of the working fluid 112 is absorbed by at least one wick structure 124, which can abut an interior surface 120 of the sealed housing 102. The wick structure 124 may be any appropriate material including, but not limited to, sintered porous structures (such as porous copper structures), gauzes (such as bronze mesh), wires, and the like. The liquid phase of the working fluid 112 is then transported from the condensation region 122 by the wick structure 124 in the direction illustrated by arrows 126 to an area proximate the dispersion device 108. The liquid phase of the working fluid 112 returns to the dispersion device 108, which disperses the working fluid 112 as a liquid spray toward the heat generating device 106 perpetuating the evaporation/condensation cycle described.

In an embodiment of the present invention, the heat dissipation device 100 is oriented such that the liquid phase working fluid drips onto the dispersion device 108 (shown as arrows 118), such as shown in FIG. 1. It is understood that the heat dissipation device can be placed in any position with respect to gravity. However, for alternate orientations, it is preferred that the wick structure 124 lines the sealed housing interior surface 120 (shown in FIG. 2 as heat dissipation device 150) to ensure effective operation. As shown in FIG. 3, it is also understood that a heat dissipation device 160, can be oriented in a vertical configuration such that the liquid phase 152 of the working fluid 112 moves along arrows 152 substantially in the direction of gravitational pull 130. The vapor phase of the working fluid 112 moves substantially in the direction shown as arrows 154. No wick structure is used with such a thermosiphon configuration, except that in some cases a boiling structure 156 may be required, as will be understood by those skilled in the art.

In an embodiment of the present invention, a heat sink (such as a plurality of high surface area, thermally conductive projections 128) may extend from a second external portion 132 of the sealed housing 102 proximate the condensation region 122. Thus, the heat absorbed by the sealed housing 102 proximate the condensation region 122 is conductively transferred to the conductive projections 128. The high surface area thermally conductive projections 128 allow heat to be convectively dissipated from the projections 128 into the air surrounding the heat dissipation device 100 (referring back to FIG. 1). High surface area conductive projections 128 are generally used because the rate at which heat is dissipated is substantially proportional to the surface area of the high surface area conductive projections 128. The conductive projections 128 may be constructed of highly conductive material including, but not limited to, copper, copper alloys, aluminum, aluminum alloys, and the like. It is, of course, understood that the high surface area conductive projections 128 may include, but are not limited to, elongate planar fin-like structures and columnar/pillar structures.

In an embodiment of the present invention, a divider plate 134 may positioned within the sealed housing, which substantially separates the vapor phase of the working fluid 112 from the liquid phase of the working fluid 112, thereby essentially dividing the sealed housing 102 into a vapor path chamber 136 and a liquid path chamber 138. The divider plate 134 assists the vapor phase of the working fluid 112 move toward the condensation region 122 and assists the liquid phase of the working fluid 112 move toward the dispersion device 108. The divider plate 134, in one embodiment, separates an inlet side 142 of the dispersion device 108 from an outlet side 144 of the dispersion device 108 in order to prevent the vapor phase of the working fluid 112 circulating through the dispersion device 108. In one embodiment, the divider plate 134 can substantially abut the wick structure 124, so that the pressure differential created by the dispersion device 108 assists in pulling the liquid phase of the working fluid 112 through the wick structure 124 toward the dispersion device 108.

The dispersion device 108 may be a water-proof or “liquid”-proof, flat rotary fan with no hub or at least a very small hub and separates at least a portion of the vapor path chamber 136 from a portion of the liquid path chamber 138. A flat rotary fan has its motor located the fan periphery. The dispersion device 108 may comprise a rotor consisting of two flat washers with a magnet therebetween and a stator comprising a printer circuit board placed in a gap between the washers of the rotor. Power for the dispersion device 108 is delivered from an external source (not shown). As previously discussed, the dispersion device 108 distributes the working fluid 112 as a substantially uniform film on the vaporization region 114. A substantially uniform spray distribution of the working fluid 112 assists in having the vaporization region 114 substantially “wet” during operation, suppression of bubble formation, and having only a thin liquid film collecting in the vaporization region 114.

A thermally insulation material 146 may be placed abutting at least a portion of an outside surface 148 of the sealed housing 102. The thermally insulation material 146 assists in preventing the condensation of the vapor phase of the working fluid 112 on the sealed housing 102 walls within the vapor path chamber 136 and from vaporizing within the liquid path chamber 138 (from potential external heat).

Although the dispersion device 108 is described as “blowing” the liquid phase of the working fluid 112 toward the vaporization region 114, it has been found that the dispersion device 108 can spin in the opposite direction and still be effective, as shown in FIG. 4. The working fluid 112 is vaporized in the vaporization region 114. The vapor phase of the working fluid 112 substantially follows the direction shown as arrows 162 to the condensation region, where is condenses into the liquid phase of the working fluid 112. The wick 124 transports the liquid phase of the working fluid 112 from the condensation region 122 substantially along the direction of arrows 164 to the vaporization region 114.

It is, of course, understood that although the present detailed description discusses the heat generating device 106 in terms of a microelectronic device, it may be anything which generates heat. Furthermore, although the heat dissipation devices 100, 150, 160, and 170 are shown with a specific configuration in FIGS. 1, 2, 3, and 4, respectively, it is, of course, understood that all of the components of the heat dissipation devices 100, 150, 160, and 170 may take on any appropriate configuration and shape.

The microelectronic device assemblies formed by the present invention may also be used in a computer system 210, as shown in FIG. 5. The computer system 210 may comprise an substrate or motherboard 220 with at least one heat dissipation device 100, 150, 160, and 170 as described above, abutting a microelectronic device (not shown), including but not limited to, a central processing units (CPUs), chipsets, memory devices, ASICs, and the like, within a housing or chassis 240. The external substrate or motherboard 220 may be attached to various peripheral devices including inputs devices, such as a keyboard 250 and/or a mouse 260, and a display device, such as a CRT monitor 270.

Having thus described in detail embodiments of the present invention, it is understood that the invention defined by the appended claims is not to be limited by particular details set forth in the above description, as many apparent variations thereof are possible without departing from the spirit or scope thereof. 

1. A heat dissipation device, comprising: a sealed housing having a vaporization region within said sealed housing and a condensation region within said sealed housing; a working fluid disposed within said seal housing; and a dispersion device disposed within said sealed housing, said dispersion device being adapted to disperse said working fluid.
 2. The heat dissipation device of claim 1, wherein said dispersion device disperses said working fluid toward said sealed housing vaporization region.
 3. The heat dissipation device of claim 1, further including a divider plate dispose within said sealed housing, wherein said divider plate substantially divides said sealed housing into a vapor path chamber and a liquid path chamber.
 4. The heat dissipation device of claim 3, wherein said divider plate abuts said dispersion device.
 5. The heat dissipation device of claim 1, further including at least one wick structure.
 6. The heat dissipation device of claim 5, wherein said at least one wick structure abuts an interior surface of said sealed housing.
 7. The heat dissipation device of claim 6, wherein said at least one wick structure extends from at least a position proximate said condensation region to at least a position proximate said dispersion device.
 8. The heat dissipation device of claim 1, a thermally insulative material on at least a portion of an exterior surface of said sealed housing.
 9. The heat dissipation device of claim 1, a heat sink on an exterior of said sealed housing proximate the condensation region.
 10. An assembly, comprising: a heat generating device; a sealed housing having a vaporization region within said sealed housing and a condensation region within said sealed housing, wherein said heat generating mechanism abuts an exterior surface of said sealed housing proximate said vaporization region; a working fluid disposed within said seal housing; and a dispersion device disposed within said sealed housing, said dispersion device being adapted to disperse said working fluid.
 11. The assembly of claim 10, wherein said heat generating device comprises a microelectronic device.
 12. The assembly of claim 10, wherein said dispersion device disperses said working fluid toward said sealed housing vaporization region.
 13. The assembly of claim 10, further including a divider plate dispose within said sealed housing, wherein said divider plate substantially divides said sealed housing into a vapor path chamber and a liquid path chamber.
 14. The assembly of claim 13, wherein said divider plate abuts said dispersion device.
 15. The assembly of claim 10, further including at least one wick structure.
 16. The assembly of claim 15, wherein said at least one wick structure abuts an interior surface of said sealed housing.
 17. The assembly of claim 16, wherein said at least one wick structure extends from at least a position proximate said condensation region to at least a position proximate said dispersion device.
 18. The assembly of claim 10, a thermally insulative material on at least a portion of an exterior surface of said sealed housing.
 19. The assembly of claim 10, a heat sink on an exterior of said sealed housing proximate the condensation region.
 20. An electronic system, comprising: a substrate within a housing; at least one microelectronic device attached to said substrate; a heat dissipation device, comprising: a sealed housing having a vaporization region within said sealed housing and a condensation region within said sealed housing; a working fluid disposed within said seal housing; and a dispersion device disposed within said sealed housing, said dispersion device being adapted to disperse said working fluid; and an input device interfaced with said substrate; and a display device interfaced with said substrate.
 21. The electronic system of claim 20, wherein said dispersion device of said heat dissipation device disperses said working fluid toward said sealed housing vaporization region.
 22. The electronic system of claim 20, wherein said heat dissipation device further includes a divider plate dispose within said sealed housing, wherein said divider plate substantially divides said sealed housing into a vapor path chamber and a liquid path chamber. 